长焦数码相机就是拥有长焦镜头的数码相机。镜头的焦距一般用毫米来表示,例如我们常说的35mm的镜头,50mm的镜头,135mm的镜头等等。镜头根据它的焦距可以分为广角镜头、标准镜头和长焦镜头等等,其实这是根据镜头的视角。在35mm胶卷里,50mm的镜头其透视程度相当于人眼(但是其视野大小比人眼的视角小得多),我们将它的放大倍率规定为一,我们把它称为标头。
只有将在最长的长焦相机的设置使用,以避免晕。
It is only to be used at the longest telephoto setting of the camera in order to avoid vignetting.
然后就是相机、长焦镜头、带摄像头的手机。
Then there is the camera, the telephoto lens, and the cellphone with a camera.
限制因素之一就是观察角度,这与使用照相机的情况类似:长焦镜头的视野比广角镜头的观察角度要窄得多。
One limiting factor is the viewing Angle, which is comparable to using a camera lens: a telephoto lens has a narrower view than a wide-angle lens.
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